Multilayer Optical Waveguides for High-Volume AR Grating Transfer
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Solution Overview
Problem
Existing methods for fabricating high-index sub-wavelength gratings and nanostructures are inefficient for high-volume and low-cost production, and there is a need to maximize the refractive index of templated nanostructures for optical waveguides in augmented reality devices.
Innovation Solution
A transfer film approach is used to fabricate high-index TiO2 sub-wavelength structures on a polymeric template, which are then transferred to a final substrate using roll-to-roll processing, with a multilayer grating structure comprising an inorganic undulating layer and a planarizing adhesive layer to enhance optical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional fabrication methods are used for high-index sub-wavelength gratings, then manufacturing precision can be achieved, but productivity is low and cost is high
Solution Approach 1:
The patent applies preliminary action by pre-forming the grating structure on a release layer before transferring to the final substrate. The multilayer grating is fabricated on a temporary carrier with release layer, allowing complex structures to be created in advance using precise methods, then transferred efficiently to multiple waveguide substrates through roll-to-roll processing, resolving the contradiction between precision fabrication and high-volume production
Solution Approach 2:
The patent uses a release layer as an intermediary between the grating structure and the waveguide substrate. This release layer enables the pre-fabricated multilayer grating to be temporarily held on a carrier, then transferred to the final substrate, facilitating high-volume production while maintaining manufacturing precision through controlled transfer processes
2Reliability
If the inorganic layer thickness is increased to maximize refractive index contrast, then optical performance is improved, but the layer becomes difficult to conformally coat and integrate
Solution Approach 1:
The patent segments the high-index structure into a multilayer grating with alternating high-index and low-index layers. This segmentation allows conformal coating of thinner individual layers that are easier to manufacture, while the cumulative effect of multiple high-index layers maintains the necessary refractive index contrast for optimal optical performance, resolving the contradiction between optical performance and ease of manufacture
Solution Approach 2:
The patent creates a composite multilayer structure combining high-index inorganic layers with low-index organic layers. This composite approach achieves high effective refractive index contrast through the periodic arrangement of materials with different indices, while each individual layer remains thin enough for conformal coating, resolving the contradiction between optical performance and ease of manufacture
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method enables high-volume, low-cost production of optical waveguides with improved optical performance by maximizing the refractive index contrast, suitable for augmented reality devices.
Implementation Method 1
The ridges and the grooves extend along an orthogonal length direction of the inorganic undulating layer. A first undulated inorganic layer is configured to receive an image light from an image projector and inject at least a portion of the received image light into the optical core.
Implementation Method 2
The injected image light propagates along the optical core primarily by total internal reflection.
Implementation Method 3
The planarizing adhesive layer is disposed between the inorganic undulating layer and the optical core and substantially planarizes one of the undulating major surfaces of the inorganic undulating layer and bonds the inorganic undulating layer to the optical core.
Data Source
AI summary
An optical waveguide (200) includes an optical core (30) configured to propagate an image light therealong, and first and second multilayer gratings (40) disposed on the optical core (30). The first multilayer grating (40a) is configured to receive an image light from an image projector (70a) and inject at least a portion of the received image light into the optical core (30). The injected image light propagates along the optical core (30) by total internal reflection. The second multilayer grating (40b) is configured to receive a portion of the injected image light and extract a portion of the received injected image light from the optical core (30) for viewing. Each of the first and second multilayer gratings (40) include an inorganic undulating layer (60) having a wave-like shape along a width direction and a planarizing adhesive layer (50) disposed between the undulating layer (60) and the optical core (30) and planarizing one of the undulating major surfaces of the inorganic undulating layer (60).